Sprinkler base unit



FIG. 1 is a right, back perspective view of a sprinkler base unit showing our new design;

FIG. 2 is a right side view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a front end view thereof;

FIG. 5 is a back end view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines illustrate environmental structure and form no part of the claimed design. 

The ornamental design for a sprinkler base unit, as shown and described. 